FRESn-WATEE SHELLS. 25 



often found in cleop clear ditches, and yields a beautiful 

 purple dye, which, however, soon becomes dull, and changes; 

 it cannot be fixed, and is therefore valueless. The mouth of 

 this shell in fine specimens, is tinged with pale violet or lilac. 



There is another kind, the Keeled Planorbis, fP. lurinatnsj 

 which has the outer edge of the shell finely ridged, or keeled; 

 it is very small, and very plentiful in fresh- water, both running 

 and stagnant; where, too, is found the Common Physa, (P. fon- 

 tinalisj the latter word meaning a spring or fountain. This 

 little mollusk is a quick and active traveller, it sometimes 

 comes out of its shell, and throws itself about in an extra- 

 ordinaiy way, keeping fast hold by its foot; the generic name, 

 Phjna, would seem to have reference to the round, smooth, 

 delicate shell, and to come from the same root as Phjsalite, 

 which means a topaz: the members of this genus are very 

 numerous, being found nearly all over the globe. The next 



belongs to the family Aurmdaclce, or Ear Shells. The Midas 

 Ear, [A. Midcd:) this handsome shell is prized by collectors; 

 it comes from the East Indies. Midas, it is said, was one who 

 set himself up for a judge of music in the old fabulous times, 

 and not appreciating that of Apollo, was rewarded by the 

 angry god with a pair of ass's ears. 



The Cone-shaped Melampus, /^M. coniiformisj also an Ear 

 Shell, is found in the rivers of the Antilles Islands. It is, a 

 pretty shell; the formation is much the same as that of many 

 of the most highly-prized varieties of Marine Shells; of these 

 we shall have to speak presently. Melcm2)odium in Latin, sig- 

 nifies a poisonous plant called Black Ilelebore; in the Mythology, 

 Melampus was a great magician, vvho did all sorts of wonder- 

 ful things; but we cannot tell what relation there exists 

 between either the plant or the magician and this pretty cone 



